JPS61250852A - Optical recording and reproducing device - Google Patents

Abstract

PURPOSE:To improve remarkably the recording density by separating the light into the major beam light and an auxiliary beam light for correcting tracking of a beam converging means and making the major beam light incident into a guide path having a transmission region shaped sharply toward the scanning track at the tip so as to converge the major light largely. CONSTITUTION:A laser ray oscillated from a semiconductor laser 7 is separated into the main beam lights beta and the auxiliary beam lights gamma, delta by a beam shap ing means 2. Then the main beam light forms a spot having a diameter of nearly 1.6mum on an upper face 19b of the transmission region of the guide path 18 by a hologram lens and the spot is narrowered gradually while being transmitted in the transmission region 19. The light is irradiated on the scanning track of the magnetic recording medium 4 on which the lower face 19a of the transmission region is slided as a spot having a nearly 0.2mum of diameter finally. Thus, the spot diameter of the major beam light beta is narrowered remark ably by the guide path having the sharp transmission region 19.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to magnetic changes with the Curie temperature as a boundary,
The present invention relates to an optical recording and reproducing apparatus that records or erases information on a recording medium using changes in refractive index caused by applying an electric field, and reproduces information by irradiating the recorded recording medium with a laser beam.

[Conventional technology]

In recent years, various optical reproducing devices have been developed that can reproduce information recorded on a recording medium using a laser beam by irradiating it with a laser beam.

As shown in FIGS. 6 and 7, for example, this optical reproducing device irradiates a laser beam oscillated from a semiconductor laser a onto a recording medium c using an objective lens b so that the laser beam is focused on the recording medium c. It is configured so that the reflected light reflected by a reflector d, which serves as a signal section in the medium C, is incident on the optical sensor r via a beam splitter e and extracted as an electrical signal, which improves the sound quality and image quality during playback. It has the feature of being

However, with this optical playback device, a complicated and expensive cutting device is used to cut the cut original disc.
After applying otoresist and exposing it according to the information,
Since this is a recording medium formed by pressing a transparent recording medium and coating it with a reflective film, protective film, etc., it is impossible to freely erase and re-record the recorded information. be.

Therefore, optical recording and reproducing involves irradiating a recording medium made of a specific material with a laser beam to cause a change in physical properties, thereby recording or erasing information, and then reproducing information by irradiating the recorded recording medium with a laser beam. A device has been proposed.

[Problem to be solved]

However, in such an optical recording/reproducing device,
There is a limit to the recording density of a recording medium, and therefore it has been difficult to record information for a long time using a recording medium having a constant diameter. This is because the laser beam is converged by an objective lens and irradiated onto the recording medium to record information, so the resolution is determined by how much the beam spot diameter can be narrowed down. It is impossible to record it.

By the way, this beam spot diameter <φ) is usually calculated as follows depending on the wavelength λ of the laser beam, the ratio of the focal length of the objective lens to the diameter of the objective lens, that is, the NA (number of functions), and the luminous intensity distribution of the laser beam light. It is uniquely determined by the relational expression φ-K·λ/NA (K: constant determined by luminous intensity distribution). Therefore, in order to increase the recording density by reducing the beam spot diameter (φ) as much as possible, the wavelength λ of the laser beam must be shortened and the Sekiguchi number (N
A) should be made as large as possible.

However, the number of entrances (NA) is usually limited to about 0.5 due to the tolerance value for the bending of the recording medium, that is, the skew tolerance angle (α), and if it exceeds this, the skew tolerance angle (α) deteriorates rapidly.

On the other hand, regarding the wavelength λ of the laser beam, it is possible to specially prepare and use a laser oscillator that oscillates light with the shortest wavelength possible when recording information, but it is expensive when reproducing information. Semiconductor lasers are generally used due to their size, weight, etc. When using semiconductor lasers, they usually emit light with a wavelength of about 0.8μ, so the recording density is higher than this. It was difficult to increase the

The purpose of the present invention is to eliminate the above-mentioned conventional problems, and more specifically, to provide an optical recording/reproducing device with high recording density.

[Means and operations for solving the problem] That is, the optical recording and reproducing apparatus of the present invention includes a laser oscillator that oscillates a laser beam, a laser beam that is formed from the laser beam, and a beam that is formed from the laser beam. A beam forming means for dispersing light into a main beam light and an auxiliary beam light, supported by a casing of the beam forming means, and an objective lens for converging the main beam light and the auxiliary beam light, and a lower surface side of the recording medium. a beam converging means comprising a waveguide sliding on the scanning track and provided with a pointed transmission region for focusing and transmitting the main beam; and a tracking correction means for correcting the deviation of the beam converging means from the operation track, and records and erases information on the recording medium by physical property changes caused by laser beam irradiation, and erases information on the recording medium. Information is reproduced by irradiating the medium with the laser beam. In other words, a laser beam of wavelength λ emitted from a laser oscillator is used as a main beam and a beam for erasing, recording, or reproducing recorded information. The main beam and the auxiliary beam are focused into a fixed spot diameter by an objective lens with a large numerical aperture (NA). The main beam is made incident on a waveguide with a transmission region formed into a pointed shape toward the scanning track, and when it passes through this field wave 6 path, the main beam light is greatly narrowed down and the spot diameter becomes significantly small, so it is difficult to record information. The recording density of the disc can be greatly increased, and the information recorded at high density can be reliably read and erased, and the recording capacity can be significantly increased.

〔Example〕

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a magneto-optical recording and reproducing apparatus according to the present invention. A beam forming means 2 for separating light into a beam and an auxiliary beam, and a casing 2 of this beam forming means 2
a beam converging means 3 supported by a, and a beam converging means 3
scanning tracks 5 on the magnetic recording medium 4.
It is comprised of tracking correction means 6 and the like for correcting deviations from the position.

The laser oscillator 1 uses a lightweight semiconductor laser 7 that outputs a laser beam with a wavelength λ0 (approximately 0.8 μm), and is mounted inside a casing 2a. Note that this laser oscillator 1 is a semiconductor laser 7 like this embodiment.
For example, when using a heavy item, it is sufficient to attach it separately from the casing 2a.

The beam forming means 2 includes a collimator lens 8 that converts the laser beam emitted from the semiconductor laser 7 into a parallel beam;
Ananorphic prism (ANANORPHICPRTSM) 9 that converts this parallel beam into a perfectly circular beam.
And, this beam light is divided into main beam light β and auxiliary beam light γ,
A diffraction grating 10 that separates into δ, and a main beam after reflection from among the light directed toward the magnetic recording medium 4 and the main beam β and auxiliary beams γ and δ that are polarized in a certain direction after being reflected by the magnetic recording medium 4. A polarizing beam splitter 11 that selectively separates only the light β and the auxiliary beams γ and δ upward and makes them incident on the main sensor (S) and the auxiliary sensor (circuit), and a recording medium 4 that directs the optical path of each beam light. 90' bend 90' towards
It is composed of a mirror 12 and a λ/4 plate 13 that circularly polarizes each beam light reflected by the 90° mirror 12, and is installed together with the semiconductor laser 7 inside the casing 2a. In this embodiment, since the laser beam emitted from the semiconductor laser 7 is a diverging light, the collimator lens 8 and the ananorphic prism 9 are
However, if a laser oscillator that emits parallel beam light is used, it is not necessary to provide these.

In this embodiment, the beam converging means 3 includes a cantilever 15 molded in a long shape from transparent plastic resin as shown in FIG. 2, and an objective lens 16 attached to the tip side of the cantilever 15. The rubber member 17 on the proximal end side is supported by the casing 2a via the rubber member 17 so as to be swingable. Although a hologram lens is used as the objective lens 16 in order to reduce the weight, the objective lens 16 is not particularly limited to this as long as it is a lightweight converging lens. The tip side of the cantilever 15 to which the holograms are attached is hollow inside to reduce weight.
This cantilever 1 is located near the optical axis at the center of the bottom side.
A waveguide 18 integrally molded with the waveguide 5 is provided. This waveguide 18 is for transmitting the main beam β, which is focused on the center side of the waveguide 18 by the objective lens 16, while focusing it toward the scanning track 5. As shown in FIG. 18 Galiarsenic (G
The transmission range 19 is provided by using a As ), etc., and a constant refractive index (nz: however, nl>
Aluminum gallyrsenide (AiGaAs) with nz)
) etc. to provide a non-transmission area 20. As shown in FIG. 4, the main beam β converged to a constant diameter by the objective lens 16 is reflected multiple times at the interface between the transmission region 19 and the non-transmission region 20 while passing through the transmission region 19 at the bottom surface 19a. This transmission fi 19 is formed into a truncated quadrangular pyramid with a sharp point toward the scanning track 5 so that it narrows down toward the side. Regarding the shape of this transmission region 19, the upper surface 19b is formed larger than the spot diameter of the main beam light β, and is formed into a pointed shape toward the lower surface 19a, and the size of the lower surface 19a tends to be larger than the scanning track. Of course, it is possible to use a shape such as a truncated cone as long as the width is about 5 mm. Further, the upper surface 18b of this waveguide 18 is mirror-finished to minimize irregularities, etc., in order to prevent unnecessary scattered light from being generated.

As shown in FIG. 5, the magnetic recording medium 4 includes a reflective film 22 made of aluminum or the like provided on a substrate 21 such as an acrylic plate, and coated with dysprosium (Dy) and gadolinium (Gd).
・Rare earth elements such as terbium (Tb) and iron (Fe)・
It has a three-layer structure including a recording film 23 made of a mixed material with a transition element such as cobalt (Co), and information is written using magnetic change.

The tracking correction means 6 applies a servo (automatic control) so that the main beam β is accurately irradiated onto the scanning track 5 on which information is being read, and auxiliary beams separated on the left and right positions of the main beam β are used. Light γ and δ are irradiated onto the scanning track 5, and if the scanning position deviates, it is corrected by electromagnetic force. This tracking correction means 6 uses a known one, that is, it emits the auxiliary beams β and γ with uniform intensity at all times, and when the scanning position deviates, the auxiliary beam γ is reflected by the magnetic recording medium 4. , δ is unbalanced, and an auxiliary sensor (not shown) receives the auxiliary beam lights γ and δ with different intensities, outputs a predetermined electrical signal, and operates the electromagnet (circuit). .

Although this embodiment is constructed with a magneto-optical recording/reproducing device that utilizes magnetic change as a signal, the present invention is not particularly limited to this; for example, the Kerr effect,
Of course, it is also possible to use the Pockels effect or the like as a signal.

Therefore, according to the magneto-optical recording and reproducing apparatus according to this embodiment, when reproducing recorded information, the laser beam oscillated from the semiconductor laser 7 is first divided into the main beam β and the auxiliary beam γ by the beam forming means 2. .

It is separated into δ and δ. The main beam β is then applied to the upper surface 19b of the transmission region of the waveguide 18 by approximately 1
．． A spot diameter of 6 μm is formed, and as it is not transmitted within this transmission region 19, the diameter of the spot 1 is gradually narrowed down, and finally the lower surface 19a side of this transmission region slides on the scanning track 5 of the magnetic recording medium 4. It is irradiated with a spot diameter of approximately 0.2 μm. When the irradiated main beam light β is able to enter and pass through the recording film 23 from the scanning track 5, it is reflected by the anti-tlJ film 22, then travels backward along the same optical path and passes through the polarizing beam splitter 11. The light is incident on the main sensor (S) for detecting main beam light β.

As described above, according to the optical recording device according to this embodiment, the spot diameter of the main beam β is significantly narrowed to about 115 mm by the waveguide 18 having the pointed transmission region 19. Therefore, the recording density can be greatly increased, and recorded information can be reliably reproduced from the high-density magnetic recording medium 4.

〔effect〕

As described above, according to the optical recording/reproducing apparatus according to the present invention, the spot diameter can be narrowed down significantly by using the waveguide having a pointed transmission range.In other words, information can be recorded, erase.

The degree of resolution of the light used for reproduction can be dramatically increased, and as a result, high-density recording, erasing, and reproduction become possible.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing a magneto-optical recording and reproducing apparatus according to the present invention, FIG. 2 is a schematic perspective view showing the configuration of a beam converging means according to the present invention, and FIG. FIG. 4 is a schematic perspective view showing the configuration, FIG. 4 is an optical path diagram showing how the main beam light is transmitted within the transmission region of the waveguide in FIG. 3, and FIG. 5 is a diagram showing the configuration of the magnetic recording medium etc. according to the present invention. The schematic perspective views, FIGS. 6 and 7, show a conventional type of optical reproducing device. FIG. 6 is an explanatory diagram showing the incident and reflected optical paths of the laser beam on the recording medium, and FIG. It is an explanatory view showing spots of laser beam light irradiated by a lens. 1... Laser oscillator, 2... Beam forming means, 2a... Casing, 3...・・・
...beam focusing means, 4...magnetic recording medium,
5... Scanning track, 6... Tracking correction means, 7... Semiconductor laser, 10...
... Diffraction grating, 11 ... Polarizing beam splitter, 13 ... λ2/4 plate, 15 ...
...Cantilever, 16...Objective lens,
18... Waveguide, 19... Transmission range,
20...Non-transmission region, 21...Substrate, 22...Reflection film, 23...
・Recording film, β... Main beam light, γ, δ・
...Auxiliary beam light. Applicant NEC Home Electronics Co., Ltd. Agent Patent Attorney Masu 1) Takeo Figure 1 Figure 2 Figure 6 Figure 7

Claims (1)

[Claims] 1. A laser oscillator that oscillates a laser beam, a beam forming means that forms a beam from the laser beam and disperses the beam into a main beam and an auxiliary beam; supported by a casing of the means, comprising an objective lens for converging the main beam light and the auxiliary beam light, and whose lower surface side slides on the scanning track of the recording medium;
and a beam converging means comprising a waveguide provided with a pointed transmission region for focusing and transmitting the main beam light, and an operation track for the beam converging means provided on both sides of the beam converging means, using the auxiliary beam light. and a tracking correction means for correcting the deviation from the recording medium, recording and erasing information on the recording medium by changes in physical properties caused by laser beam irradiation, and irradiating the laser beam on the recording medium on which information has been recorded. What is claimed is: 1. An optical recording and reproducing device characterized in that information is reproduced by